Brooklyn is under siege.

Enemy combatants dressed in all-black riot gear roam the streets, gunning down any citizen that gets in their way, setting fires, blowing up cars, going from house to house and apartment to apartment, taking the Bushwick neighborhood one block at a time.

Not that the residents aren’t putting up a fight. Oh, they’re putting up a fight and then some. They’ve got guns and they’ve got knives and they’ve got baseball bats and they’ve got the will to survive, and they’re engaged in full-out war with these unnamed invaders.

This is the setup for “Bushwick,” a tight, intense, relatively low-budget thriller that plays like a video game, with a college student played by Brittany Snow (“Pitch Perfect”) and an Iraq veteran played by Dave Bautista (the “Guardians of the Galaxy” movies”) as the two main avatars.

Co-directed with a loose, suitably chaotic style by Cary Murnion and Jonathan Milott (working from a sharp and sometimes darkly funny script by Nick Damici and Graham Reznick), “Bushwick” is set in the present day, but it’s reminiscent of past-generation actioners such as “Red Dawn” and “Assault on Precinct 13” and “Escape from New York.” Even the sometimes ear-splitting, techno-rock score is reminiscent of 1980s thrillers.

Snow’s Lucy is a college student returning home to Bushwick to introduce her boyfriend to her family. When they step off the train, the station is abandoned and eerily quiet — and when they ascend the stairs, they’re plunged into the middle of a chaotic battle, with drones and helicopters flying overhead and those mysterious militia forces facing off against the locals.

Let’s just say Lucy is once again single within minutes.

As the bodies pile up, Lucy finds herself in the company of Stupe (Bautista), a hulking janitor and former military man with mad fighting skills. (Bautista was once a WWE star, and he has the opportunity to execute a couple of fantastically entertaining body slams through the course of the day.)

Stupe and Lucy bond after the obligatory “amateur triage” scene where Stupe has to yank a six-inch shard of glass from his leg (in grotesque close-up, of course), and then Lucy has to help him cauterize the wound. (Later, it’s Lucy who needs emergency medical attention when a gunman blows off the third finger on her left hand. “Oh my God, what am I going to do when I get married?” she cries.)

Stupe wants to make it back to Hoboken and his wife and child. Lucy wants to check in on her grandmother and on her perpetually high sister Belinda (Angelic Zambrana). At one point they capture an enemy soldier, unmask him, and learn …

SPOILER ALERT!

He’s from Kentucky.

Turns out a number of Southern states seceded from the Union and they’re fighting “for the right to live our lives the true American way,” as the so-called soldier puts it. “We’re a private Army.”

And why have they invaded this particular area? According to this idiot, Brooklyn “was a designated soft spot because of its ethno-diversity. There weren’t supposed to be so many guns.”

Responds Belinda: “Welcome to New York, you stupid m———–.”

As the camera follows Lucy and company through the streets in long tracking shots, the co-directors sprinkle in numerous incidental but eye- and ear-catching moments.

We see a group of four Hasidic Jews with shotguns, mowing down militia members in an alley. We hear a group of protesters chanting, “Whose streets? Our streets!” We meet a priest who has gone mad after witnessing so much carnage.

Some of the big reveals in “Bushwick” seem arbitrary. And the ending, while true to the nature of the story, is deeply unsatisfying. What could have been a great B-movie winds up being merely solid.

★★★

RLJ Entertainment presents a film directed by Cary Murnion and Jonathan Milott and written by Nick Damici and Graham Reznick. No MPAA rating. Running time: 94 minutes. Opens Friday at AMC Woodridge and on demand.